São Luís (Saint Louis) is the capital and largest city of the Brazilian state of Maranhão. The city is located on Ilha de São Luís (Saint Louis' Island) in the Baía de São Marcos(Saint Mark's Bay), an extension of the Atlantic Ocean which forms the estuary of Pindaré, Mearim, Itapecuru and other rivers. Its coordinates are 2.53° south, 44.30° west. The city proper has a population of some 986,826 people (2008 IBGE estimate). The metropolitan area totals 1,227,659, ranked as the 16th largest in Brazil.

São Luís, created originally as Saint-Louis, is the only Brazilian state capital founded by France (see France Équinoxiale) and it is one of the three Brazilian state capitals located on islands (the others are Vitória and Florianópolis).